Re: Inflationary Theory ; I'm confused

From: George Dishman (george_at_briar.demon.co.uk)
Date: 02/20/05 

Date: Sun, 20 Feb 2005 20:23:21 -0000

I'll snip some older stuff to reduce the length.

"TomGee" <lvlus@hotmail.com> wrote in message
news:1108920153.225508.148710@c13g2000cwb.googlegroups.com...
>
> George Dishman wrote:
>> "TomGee" <lvlus@hotmail.com> wrote in message
>> news:1108743767.544269.163600@l41g2000cwc.googlegroups.com...
<snip>
>> > I appreciate your point. I ascribed the term "parallel" on my own to
>> > his explanation of curved space as printed in several publications
>> > through the years. I never read where he said it was the same universe
>> > as ours.
>>
>> If you think of it the other way round, since he was
>> describing our universe why would he bother saying it.
>> Remember he was writing in 1905 and ideas like "parallel
>> universes" were far in the future.
>>
>>
> No, I think he would have said "in our universe" so as to make certain
> for posterity what he was referring to, since he knew ours is a 4d
> universe. He may have invented the parallel universe idea or helped
> plant it in other's minds.

Perhaps you should read the first few paragraphs of
the paper:

http://www.fourmilab.ch/etexts/einstein/specrel/www/#tex2html1

I can't see anything suggesting he was talking of, or
planting the idea of parallel universes.

AFAIK the idea came from the MWI of QM but I could be
wrong, but certainly the 1905 paper was not talking
of "parallel universes".

>> > More recently, Stephen Hawking wrote in his book, "A Brief History Of
>> > Time", page 24, that "It is often helpful to think of the four
>> > coordinates of an event as specifying its position in a
>> > four-dimensional space called space-time. It is impossible to imagine
>> > a four-dimensional space." Here, even Hawking refers to s-t as if it
>> > were a parallel U.
>>
>> I can see how you might read it that way. It's always
>> difficult to throw off a false impression like that
>> when you have no doubt interpreted everything you
>> read since in that way. Oh well, all I can say is
>> rest assured he was talking of our universe, not a
>> parallel one.
>>
>>
> I don't think I got a false impression. I think he meant to hedge his
> bets on that. He seemed to get quite good at that through the years.
> In order for me to rest assured he meant our universe, I would need to
> see where he actually said that he referred to our universe and not one
> where his so-called space-time continuum exists. His s-t universe does
> not exist in our universe, so I think that should lead us to think he
> referred to somewhere else, like in our minds.

"Spacetime" wasn't Einstein's term, nor at that time was
he even thinking of the universe in that sort of way.

>> > However,
>> > having said that, my model does claim that dark matter is essentially
>> > static in space. Waves move through space, and so does visible matter,
>> > but invisible matter stays in place in space.
>>
>> Relativity says the concept of "static in space" is
>> meaningless.
>>
>>
> Yes, but I am not talking Relativity here, I refer to my model which
> adds to the ideas about which Relativity has only raised questions.
>>
>>
>> In SR any inertial frame can arbitrarily
>> be called "static" and everything else is moving in
>> that frame. GR extends that to accelerated frames.
>> Hence the implication, if "moving through space" is
>> to mean anything, there should exist some special
>> condition which could be described as static against
>> which the motion is to be measured.
>>
>>
> Yes, of course, but that is true only when one wishes to measure
> motion. It is not necessary to measure motion in order to see an
> object moving.

They are the same. You can just as easily "see" the
object and you as moving past it. Anyway, isn't this
a sidetrack?

> AE said that "motion is meaningful only to two bodies",
> but he contradicted that by saying that space and time are
> interdependent and dependent on the motion of observers. That means
> there is at least one more thing to which motion is meaningful.

I don't know why you think there is a contradiction.
If you follow the idea of a 4D manifold then space
is a (3D) slice perpendicular to the chosen time axis
and motion is the angle between an object's worldline
and the coordinate time axis so "motion is meaningful
only to two bodies" is saying motion can only be
defined relative to the observer (to establish the
coordinate time axis), the reason being that "space
and time are interdependent".

>> > But Hawking said that is impossible.
>>
>> If you mean the quote above, he said it was impossible
>> to _imagine_ or perhaps visualise would be a better word.
>>
> How would that be a better word if they mean the same thing? Is that
> like calling invisible matter "Dark Matter" so as not to use the word
> "invisible"?

Better because it avoids a possible ambiguity in the
language, fairies must be imagined but bricks are
real. Visualising a brick is dealing with something
real whereas fairies can only be imagined.

>> > But, if it wasn't, I assume you
>> > mean above "at a fixed rate" IN TIME but not necessarily at a fixed
>> > rate of speed, no?
>>
>> It means at a fixed rate through spacetime. The rate
>> through time and through space are then related in a
>> manner similar to Pythagoras' Theorem. The combination
>> of the two rates always produces the speed of light.
>>
>>
> But again, spacetime is not real,

But again, yes it is. It is the name given to the 4D
universe in which we live.

> so the real rocketship on the real
> Earth is not REALLY moving through the curved space of Earth, is it?

Earth stays in orbit because the Sun curves spacetime.

> The ship cannot fit on the little *** of paper you are using to track
> its world line, does it? And of course, neither can the Earth fit on
> it.

Of course not, but a drawing of spacetime isn't
spacetime.

<snip>
>> <snip>
>> >> All of physics consists of mathematical models of the
>> >> world around us. Ohm's Law says voltage equals current
>> >> times resistance. Ohm's Law is a mathematical model of
>> >> a resistor, it isn't actually a resistor. Relativity is
>> >> no different in this respect.
<snip>

>> > We know that
>> > different paths from an event may have different lengths, but that
>> > knowledge is based on the Principle of Equivalence and not on s-t.
>>
>> http://aether.lbl.gov/www/science/equiv.html
>>
>> I don't see the relevance. Are you perhaps thinking
>> of the invariant interval?
>>
>>
> No. I meant that physical laws apply the same to all in the universe
> in that different-length paths are not inclusive to a fictional s-t.

The Principle of Equivalence says there is no way of
distinguishing between the effects on an observer of
a uniform gravitational field and of constant
acceleration.

>> > math. If it was based on math, we would have to believe that s-t
> is a
>> > real place.
>>
>> It is. We live in it.
>>
>>
> If you do, you live in an imaginary place.

In relativity, the term "spacetime" is used to refer
to the universe in which we live. It is not just math
and not a parallel universe. The math of SR and GR
describe this real universe in which we live. Of
course I can't comment on your ideas.

> No, wait, it must be a
> philosophical place since you believe that s-t is a philosophical point
> of view, no?

Not quite. There is a philosophical aspect regarding
how we distinguish our perception of the progression
of time but that is a question of interpretation and
gets quite complex. It might be better to leave that
for another day rather than cloud the simpler issues.

>> > Which curved lines, George?
>>
>> The lines described by a family of free-falling
>> objects, geodesics I believe, as I said later.
>>
> Geodesics is a math construct, George, imaginary lines.

Yet again, see my comments, still quoted above,
regarding Ohms Law.

>> >> and it is forced to lie along the surface of the
>> >> cylinder.
>> >>
>> >>
>> > As the cylinder moves through time,
>>
>> The axis of cylinder _is_ time.
>>
>> > yes, but the cylinder is imaginary,
>>
>>
>> It is in our imagination but it is a visualisation
>> of reality. As you said, most people know we live
>> in a 4D universe. All I have done is ignore the
>> north-south direction so that you can more easily
>> visualise the remaining three. As Hawking said in
>> your quote above, "It is impossible to imagine a
>> four-dimensional space." I have seen a few people
>> say they can do it but it's certainly very hard.
>>
>>
> To visualize something is to imagine it, George.

Right, but the thing being visualised may be real
(e.g. a brick) or imaginary (e.g. a fairy). That's
an ambiguity which I have seen cause confusion and
IMHO using 'visualise' instead of 'imagine' reduces
that risk.

>> > George, and so the rocketship is not really moving through the curved
>> > space of the earth, is it? Everyone knows that while it sits on Earth,
>> > it then is also moving through time, as is the planet and all of us
> on
>> > it, but that does not mean it is moving through the curved space of
>> > Earth.
>>
>> It is moving through spacetime which is curved by
>> the gravity of the Earth (and Sun etc.).
>>
>>
> But s-t is not where Earth and us are, since we are real and it is not.

But it is. You are confusing the equations of GR which
describe spacetime with spacetime itself which is real,
just like confusing Ohm's Law with a resistor.

>> With the possible exception of a few post-Newtonian
>> variants that are observationally indistinguishable,
>> it is the only model of the universe we live in that
>> accurately describes gravity. It is a model that
>> reflects the currently accepted view of reality.
>>
>>
> I no longer think that is true, but even if it was, that's the same
> argument used against Galileo and others who rejected "currently
> accepted" views of reality.

That's why I was careful to say "With the possible
exception of ..." and "currently accepted". Many
of the best scientists are working to replace it
and with luck perhaps a better formulation will be
found in my lifetime. However, Newton's ideas lasted
a couple of centuries and Einstein's are close to
that (1915 for GR) so don't hold your breath ;-)

George

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